These eight original questions test the four skills from this cluster, from simple graph readings to a mixed task. Try each before opening its answer.
Return to wave and image interpretation if you need the lessons. For the wider chapter, use the waves practice set.
Questions
Q1. A displacement-time graph has peaks at +6 cm and troughs at −6 cm. State the amplitude.
Answer
The amplitude is measured from the equilibrium line to a peak, so it is 6 cm. The peak-to-trough value of 12 cm is twice the amplitude.
Q2. On a displacement-time graph, 5 complete oscillations take 0.10 s. Find the period and frequency.
Answer
T = 0.10 ÷ 5 = 0.020 s. f = 1 ÷ 0.020 = 50 Hz.
Q3. Wave X and wave Y have the same period, but Y has half the amplitude of X. What is the same, and what is different?
Answer
The period and therefore the frequency are the same. The amplitude is different: Y is half of X. The height changed, but the horizontal spacing did not.
Q4. A displacement-time graph shows a period of 0.025 s. The wave speed is 20 m/s. Find the wavelength.
Answer
f = 1 ÷ 0.025 = 40 Hz. λ = v ÷ f = 20 ÷ 40 = 0.50 m. The 0.025 on the graph is a time, so it cannot be the wavelength.
Q5. A convex lens has f = +8 cm. An object is at u = 12 cm. Find v and describe the image.
Answer
1/v = 1/8 − 1/12 = 3/24 − 2/24 = 1/24, so v = +24 cm. The image is real and inverted. m = 24 ÷ 12 = 2, so it is magnified.
Q6. A concave lens has f = −10 cm and the object is at u = 15 cm. Find v and describe the image.
Answer
1/v = −1/10 − 1/15 = −3/30 − 2/30 = −5/30 = −1/6, so v = −6 cm. The image is virtual, upright and diminished. m = 6 ÷ 15 = 0.4.
Q7. Waves with wavelength 2 cm pass through a gap of 10 cm, then through a gap of 2 cm. Compare the two results.
Answer
The 2 cm gap gives strong diffraction because the gap equals the wavelength. The 10 cm gap gives little diffraction because it is five times the wavelength. The wavelength, speed and frequency stay the same in both.
Q8. A displacement-time graph shows 8 oscillations in 0.40 s. The wave travels at 10 m/s. Find the wavelength, then state what would happen to the diffraction at a gap of 0.10 m.
Answer
T = 0.40 ÷ 8 = 0.050 s, so f = 20 Hz. λ = 10 ÷ 20 = 0.50 m.
A gap of 0.10 m is smaller than the wavelength, so the wave diffracts strongly and spreads widely. The wavelength stays 0.50 m after the gap.
If you got these wrong
Q1 to Q3 point to the amplitude and frequency lesson. Q4 and Q8 need the time-axis lesson.
Q5 and Q6 are covered in the lens sign convention lesson. Q7 links to explaining diffraction.
Use the timed practice session builder to repeat under time, and see online one-to-one Physics tuition for teacher support.